Polarized relay.



J. L. WO0DBRIDGE.`

POLARIZED RELAY. APPLIUATIONTILBD 11.111. 21. 1910.

1,042,183.. muted 001.122, 1912.

E u {jy-L www wmlfss I 1 n mmf/mw JOSEPH LESTER-WO0DBBIDGE, QF-PHILADELPHIA, PENNSYLVANIA.

PoLanIzun RELAY.

Specification of Letters latentfT Patentedoct. 22,1912.

Application led'arch 21, 1910. Serial No. 550,685.

To all whom it may concern:

Be it known that I, JosErH LESTER Woon- ERIDGE, a citizen of the UnitedStates, and residing in the city of Philadelphia, State of Pennsylvania,have invented certain new and useful Improvements in Polarized Relays,of which the following is a specifica tion.

v rIlhis invention comprises certain improvements in the design ofpolarized relays or similar electromagnetic devices, which are designedto respond to small reversals of current in a given circuit, o r in somecases to smallvariations of current on either side of a predeterminedvalue, and are arranged to discriminate between a fioW of current` inopposite directions in the said circuit, so

as, for example, to close a certain contact* when the current is in onedirection and open said contact and close another contact when thecurrent is in the opposite direction. l

One of the principal objects of my invention is to reduce the size ofthe polarizing coil required when the current strength in the coil towhich the device is responsive varies over a wide range.

The nature of my invention Will be more clearly understood by referenceto the following description taken in connection with j the accompanyingdrawing, in whichf A is the armature of an electromagnet, pivoted at Xand carrying a conducting tongue T, which is connected at one end to thecircuit 3, and may make contact at the other end with either of thecontacts l or 2 according lto the position of the armature A. Thearzrature is held in one position by the yretractive spring H,adjustable by the screw J and may be drawn into the other position bythe attraction of the magnet when properly excited. The design of such acontact device is well known and it may be applied to a variety ofpurposes well understood. .i

The stationary portion of the electromagnet includes two magnetic pathsB and C, arranged in parallel relation with yeach other and with thearmature A, these three being thus connected in parallel by the membersL L and M M of the magnetic circuit. -The magnetic path B is interruptedby an air gap D, while the magnetic path C is interrupted by an air gapE. The object of these'air gaps will be explained later,

" and it will be, understood that they may be filled by any non-magneticmaterial, such as brass, in order to facilitate the mechanicalconstruction of the apparatus.

The magnetic path B is excited by the polarizing coil G shown insection, while between the paths B and C is a conductor or electrlccircuit shown in section at F.y This i divide as shown by the arrows, apartpassing through the path C and the air gap E ,and another partpassing vthrough the arma. ture A and the air gap I. The adjustment maybe such that with the excitation of the coil (l alone and no current inconductor F, the force exerted on the armature A will be just balancedby the spring H and the contact tongue T will remain in a mid positionbetween contact points l and 2. If, now a small flow of current in onedirect-ion occurs in conductor F, it will increase the p ull exerted onthe armature A, overcoming the tension of the spring H and makingcontact at point 1. This flowof current will decrease they magnetism inthe pat-h vC` and also in the path B, but-will increase the magnetism inthe armature A and in the `netic lines through the path B, which willnrembers M M. If, however, a smallgllyv tween the armature and themagnet itself,

ico

very few lines of magnetic force would pass through the armature if thepath C were not interrupted by this air gap E. Similarly the air gap Dis required in order that the excitation produced by current inconductor F shall cause a change of magnetic lilies through the armatureA. Without this air gap D, the path B would act as a magneticshort-circuit and prevent any change in magnetism from taking place inthe armature A with changes o current 1n conductor F.

An important feature of the design of this electromagnet lies in therestricted section of the members L L. The object of this restrictedsection is to permit this portion of the magnetic circuit to becomesaturated when the current in F reaches a certain value so as to limitthe further increase in magnetism due to an increase in'current beyondthis value. As stated above, when the currentI in I" is in a certaindirection the lines of force produced by this current in the armature Aand the members M M will be in the opposite direction to those producedin the same portions of the magnetic circuit by the coil G, thusweakening the pull on the armature A and allowing the spring H topredominate. If the current in conductor F should continue to increasein the same direction the magnetism in the armature A and the members MM would finally be reduced to zero and then reversed, and if a suicientincrease of current should occur in F this reversed magnetism mighteventually be sufficient again to over-power the spring H and makecontact between the tongue T and the point 1, which should 'only occurwhen the current in F is in the opposite direction. If, however, thesection of the members L L is made sutiiciently small these members willbecome saturated and preventthe above results from taking place, thatis, prevent a sufficient amount of reversed magnetism from beingproduced in the armature A and the members M M to overcome the tensionof the spring H. This result may be more clearly indicated by anumerical example. Assume that the section of the path B, the members MM and the armature A to be such that the magnetic reluctance of theseportions of the iron circuit may be neglected. Assume that the air' gapI, between the armature A and the stationary portion of the magnet isone-eighth of an inch long and one square inch in section, and assumethat it is desired to transmit 15.000 magnetic lines across this airgap. This will call for approximately 585 ampere turns. Assume the airgapD to be one-eighth of an inch in length, and assume that the samemagnetic density is produced,

in this air gap. This will call for 585 more ampere turns or a total of1170 ampere turns in the coil G. A certain 'number of lines portion ofthe circuit. In order to maintain the above specified density in the airgap D its section must then be 19A; square inches, since the total of22,500 lines must pass through it. The magneto motive force applied tosend lines across the air gap I, that is, 585 ampere turns, will also beavailable to send lines through the path C and the air gap E, sincethese two magnetic circuits are in parallel. Assume that the crosssection of the members L L is such that the magnetic density is 28,000lines per square inch. As there are 7500 lines passing through thesemembers their section will be a little over one-quarter of a squareinch. It these two members aggregate 24 inches in length it will requireabout 95 ampere turns to transmit these lines through these two membersin series. There will remain 490 ampere turns available to' send 7500lines across the air gap E, and this air gap may be made 0f suitablelength and section to require this excitation.l Ve will then have withan excitation of 1170 ampere turns in the coil G, 22,500 lines throughthe path B and across t-he air gap D, of which 15,000 lines will pass inone direction through the armature A while 7500 lines will pass in theopposite direction through the a1r gap E. Assume now that we wish totransmit sutlicient current through conductor F to increase the linesin' the armature A by 10%. It will require 10% of 585 ampere turns or58% ampere turns to produce this excitation. This same excitation willreduce the density in the air gap D in the same prop ortion, and sincethe air gap D has 50% greater cross section, 50% greater increase inlines will be sent through the path B. That is, the increase of lines inthe path B will be 2250. It will be necessary, therefore, to increasethe lines across theair gap E and through the members L L by the sum ofthese two amounts or 3750. This will increase the density in theair gapE by 50% and will call for 50% more ampere turns than were required toproduce the 'original density, that is, 50% of 490 or 245. To increasethe density in the members L L by 50% will call for about 48 ampereturns. There will be required therefore a total of 351% ampere turns toproduce the above results, and as the conductor F is a single conductorit will require 351iV amperes flow of current. Similarly, if it'isrequired to reduce the magnetic density in the armature by 10% a flow of351e amperes in the opposite direction through conductor F will producethis result, since the saturation of the iron is at a very low point andthe magnetism will therefore be practically proportional to theexcitation. Now, let us determine what will call for 15,000 linesthrough the armature A and air ga I in the reverse direction to that ofthe original magnetism 1n order to neutralize, and will call for .585ampere turns to produce this result. This excita-- tion, produced by thecurrent in the conductor F, will cause an increase of 22,500 linesacross the air gap D, or a total increase of 37,500 lines across the airgap E and through the members L L. This increase in density in the airap E will produce a density of six times t e original ensity at thispoint andcall for an increase 1n magneto-motive force equivalent to fivetimes the original, that is, five times 490 or 2450. This will increasethe density in the members L L from 28,000 lines per square inch to sixtimes this amount or 168,000 lines per inch. This would call for about50,000 am-` pere turns. It will be seen, therefore, that with a devicedesigned in accordanceA with the above proportions, the polarizing ,coil

G designed for 1150 ampere turns will be sufficient toV maintain theolarization and prevent reversal of magnetlsm in the armature A, evenwith a current strength of 50,000 amperes in conductor F in thedirectionto tend to produce such reversal, this result being brought about by thesaturation of the members L L.l At the same time the apparatus issensitive to current reversals in conductor F amounting to but two orthree hundredamperes in either direction. It will be seen that 350amperes in conductor F is sufficient t-o produce a change of 10% in themagnet-ism through the armature A, and much smaller changes than thiswould be suiiicient to produce contact with either point 1 or point 2.

If it is desired that the apparatus, instead of responding to reversalsof current on either side of zero in conductor F shall respond tovariations of current in thisconductor on either side of some othervalue, a coil K may be added embracing that part of the magnetic circuitaffected by F and eX- cited to such extent that when the current in F isat the critical value the algebraic sum of the two excitations will bezero. A similar result may be obtained by varying the excitation of the:coil G or the tension of the spring J.

What I claim and desire to secure by'Letters Patent is, v

1. In combination in an electromagnet, three magnetic circuits arrangedin parallel relation, whereof the first contains a movable member, thesecond is providedfwith a polarizing coil and the thirdis provided witha source of varying excitation and includes a restricted section adaptedto permit the passage of magnetic flux to increase or diminish the fluxproduced by the polarizing coil in the movable member, but to becomesaturated to limit the reversal of said polarizing fiux. v

In combination in an electromagnet, three magnetic circuits arranged inparallel relation, whereof the first contains a movable member, thesecond is interrupted by a .non-magnetic gap and is provided with apolarizing coil and the third is provided with a source ofvarying'excitation and includes a'restricted section adapted to permitthe passage of magnetic fiux to increase or diminish the fiux producedby the polarizing coil in the movable member, but to become saturated tolimit the reversal of said polarizing flux.

3. In combination in an electromagnet, th'ree magnetic circuits arrangedin parallel relation, whereof the first contains a movable member, thesecond is interrupted by a non-magnetic gap and is vprovided with apolarizing coil and the third is interrupted by a non-magnetic gap, isprovided with a source of varying excitation and includes a restrictedsection adapted to permit the passage of magnetic flux to' increase ordiminish the fiux produced by the polarizing coil in the movable member,but to become saturated to limit the reversal of said polarizing flux.

4. A polarized electromagnetic device having conductors tending toreverse its magnetic flux, and having a magnetic path of relatively lowsaturation point which by becoming saturated limits the reversal of theflux.

5. In combination in an electromagnetic relay, a movable contact makingmember, a retractive spring to hold said member in one position, apolarizing coil adapted to produce a magnetic flux to attract saidmember against the force of said spring into another position, anelectric circuit carrying a variable current and in inductive relationthereto a magnetic pat-h, said circuitand path arranged to cooperatewith the polarizing coil Yto increase or diminish the magnetic fluxfirst mentioned with variations of current in said circuit, saidmagnetic path having a restricted section adapted to become saturated tolimit the reversal of said flux to prevent the attraction of the movableEn tesmony whereof L have hereunto e magnetism produced in the ,ls

slgned my name.

c path by he Constant excitation. I

".7. En combnaon, en eecrc circuit, and

polarized eeetomagneo device arranged OSEPE LESTER WOODBREDGE.

o to respond to changes of current in saidv cr- I cuit :1nd having amagnetic path adaped to become saturaed to mit the reversa of magneieuz: by the current in Said Circuit.

Witnesses:

JOSEHP Tri. TRACY.

